The most significant determinant of educational and clinical impairment in school-age children with autism spectrum disorders (ASD) is the frequent co-occurrence of hyperactivity and inattention symptoms. In response, clinicians treating ASD are increasingly adopting the terminology, rating scales and medication treatments established for the management of Attention-Deficit/Hyperactivity Disorder (ADHD). However, responses to stimulants are less substantial than obtained in ADHD, and with greater risk of adverse effects. This conundrum can be clarified by examining the neuronal substrates of these symptoms with novel resting state fMRI methods employed by our lab for mapping brain functional connectivity. FMRI signals contain large amplitude low frequency spontaneous fluctuations. Such fluctuations are usually ignored, but 'functional connectivity'(FC) analyses reveal strikingly consistent patterns of intrinsic synchronized activity that delineate entire functional circuits and that differ significantly in multiple psychiatric disorders. Analyzing FC during rest is well suited for studies of children with ASD or ADHD, because the absence of a task minimizes potential floor, ceiling, or practice effects. Our preliminary data demonstrate the feasibility of relating inter-individual differences in hyperactivity, inattention, and social reciprocity to indices of FC strength in key neural circuits. To address ASD heterogeneity with regard to ADHD-like symptoms, we propose relating brain FC to Social Responsiveness Scale (SRS) scores, and to parent ratings of hyperactivity/impulsivity and inattention. Building on ongoing funded studies of children with ADHD and typically developing controls (TDC) [which are already supporting half of the TDC and ADHD samples that would be included in this project], we will characterize three groups of right-handed children (n=100/group) ages 8-11 years (ASD, TDC, and ADHD) with respect to parent SRS ratings, and Conners ratings of hyperactivity/ impulsivity and inattention. Each group will be group- matched on age, sex, and socioeconomic status to address the following specific aims: (1) To determine the extent to which symptoms of hyperactivity/impulsivity and inattention in ASD can be attributed to the presence of abnormalities in the same neural circuits as in ADHD;(2) to identify neural circuits uniquely associated with symptoms of hyperactivity/impulsivity and inattention in ASD;and (3) to determine if brain correlates of social reciprocity in ASD are independent of symptoms of hyperactivity/impulsivity and inattention. If successful, we will be able to differentiate individuals with ASD-related hyperactivity and inattention with underlying pathophysiology indistinguishable from that observed in ADHD from those in whom the pathophysiology is ASD-specific. Such stratification is required for pathophysiology-guided treatment-response studies of ASD- related symptomatology, leading to targeted therapeutics in this highly heterogeneous population. Additionally, this proposal will implement an important goal of the ARRA by supporting the creation of five new full-time positions. PUBLIC HEALTH RELEVANCE: Although many school-age children with autism spectrum disorders are also hyperactive and inattentive, which further limits their school and social functioning, we have not been able to determine whether the brain processes responsible for such ADHD-like symptoms are the same as in typical ADHD or whether they reflect distinct brain processes. Using new methods to measure spontaneous brain function, we propose to disentangle these issues in three groups of children with autism spectrum disorders, ADHD, and typically developing controls. If successful, we will be able to better understand the types of brain mechanisms that are involved in hyperactivity and inattention in children with autism and then be able to use that information to guide targeted treatment studies.